1. Field of the Invention
The present invention is generally related to snorkels used by skin divers and swimmers. More particularly, this invention is related to devices that help purge water from a snorkel.
2. Description of the Prior Art
Skin divers and swimmers use the snorkel as a means to breathe while swimming face down on the water surface. The snorkel functions as a conduit between the diver's mouth and the overhead air (hereinafter “skin diver”, “swimmer” and “diver” will be used interchangeably). Typically, the open end of the snorkel conduit extends a short distance above the water surface. Occasionally, due to swimming movements or wave action, small amounts of water flow or splash into the open end of the snorkel and partially floods the conduit. An experienced skin diver can sense when water enters the snorkel and responds by immediately stopping inhalation. Respiration is resumed after the snorkel has been purged of water. Inexperienced skin divers find occasional flooding especially troublesome because, undetected, water can be inhaled resulting in coughing and extreme discomfort.
Water will also flood the snorkel when the swimmer deliberately dives below the water surface. The snorkel conduit will be completely flooded with water when the swimmer returns to the surface. When the open end of the snorkel is again above the water surface, the flooded conduit is purged for respiration by exhaling an explosive blast of air into the mouthpiece.
Surface tension forms the purging blast of air into a bubble that spans the cross section of the snorkel conduit. Pressure within the bubble expands the bubble toward the open end of the conduit. As the leading surface of the bubble moves away from the mouthpiece, the bulk of the water within the conduit is pushed ahead of the bubble and out the open end.
The purging bubble of air will slip past water that adheres to the inside surface of the conduit. After the purging air bubble is spent, residual water will flow down the inside surface toward the mouthpiece. Also, water which splashes into the open end of the snorkel conduit due to swimming movements or wave action will typically strike and adhere to the inside surface of the conduit and thereafter flow toward the mouthpiece. Water accumulates at the lowermost portion of the snorkel conduit, typically adjacent the mouthpiece, and can soon obstruct the conduit. Unless the conduit is completely blocked, a slow and cautious inhalation is possible after which another purging exhalation can be made.
The respiratory effort needed to purge a snorkel is significant. Some skin divers and swimmers lack the respiratory strength needed to completely purge a flooded snorkel with a single exhalation, and must repeat the purging procedure several times. Also, water will sometimes enter the snorkel just as the swimmer has completed an exhalation, leaving very little air in the lungs to satisfactorily complete a purge.
A popular solution places an externally directed purge valve in the snorkel conduit at a location near the snorkel mouthpiece. Water in a flooded conduit that extends above the ambient water surface will drain through a purge valve. A purge valve will drain the snorkel conduit until the water level within the conduit matches the ambient water level. Theoretically, because the total volume of water in the flooded snorkel is reduced by the initial flow through the purge valve, the respiratory effort required to purge the remaining water is also reduced.
Unfortunately, a purge valve also provides an alternate path for forcefully exhaled air. A purge valve will quickly and wastefully dissipate the explosive blast of purging air when the purge valve is located close to the mouthpiece. One solution to this problem places a purge valve in the snorkel conduit at a location approximately midway between the mouthpiece and the open end of the snorkel conduit.
At mid-length of the snorkel conduit, the purge valve will be close to the ambient water surface when the skin diver is swimming face down on the water surface. At such a location, the purge valve will drain that portion of the snorkel conduit that extends above the purge valve and the water surface, but will not initially interfere with the purging blast of air. Even at this location, the purge valve will dissipate the forcefully exhaled air and the amount of residual water adhering to the inside surface of the conduit between the purge valve and the open end will be substantial. Residual water subsequently accumulates at the lowermost portion of the snorkel conduit and obstructs the conduit. Consequently, a single purge valve, even when located mid-length of the snorkel conduit, is of limited benefit.
The applicant addressed the problems of the prior art by the teachings of U.S. Pat. No. 4,879,995 titled Snorkel for Skin Divers, filed Oct. 13, 1987 and issued Nov. 14, 1989; and continuation U.S. Pat. No. 5,092,324 titled Snorkel for Skin Divers, filed Oct. 12, 1989 and issued Mar. 3, 1992. The applicant's patents teach a conduit divided approximately mid-length by a bell-shaped chamber having a symmetrical purge valve. The purge valve is located adjacent and above the water surface when the snorkel is in use by a skin diver swimming face down on the water surface. The purge valve opens under slight hydrostatic pressure and quickly drains water from the upper portion of the conduit when the skin diver returns to the surface after swimming or diving underwater. After a purging exhalation, or after splashing into the open end of the upper conduit due to swimming movements or wave action or-the-like, the forces of molecular cohesion and adhesion cause water to flow down the inside surface of the upper conduit and chamber to the purge valve. The purge valve opens under slight hydrostatic pressure and drains the water to ambient at a rate sufficient to prevent overflow into the lower conduit. Drainage of the lower conduit is facilitated by an optional second purge valve located at the bottom of a second chamber below the mouthpiece. The lower portion of the conduit is purged for respiration by exhaling a forceful blast of air into the mouthpiece that pushes the water upward. The effort required to purge the snorkel is reduced because the bulk of the ascending water flows out the first purge valve, without the need to overflow the snorkel top. The chamber located below the mouthpiece captures residual water in the snorkel after a purging exhalation and any water that overflows the first purge valve. The second chamber also captures fluids that may drain from the swimmers mouth through the mouthpiece.
Snorkels based on the teachings of U.S. Pat. Nos. 4,879,995 and 5,092,324 have been successfully marketed to the diving and swimming community under the trade name “Impulse Snorkel”. However, swimmers have complained that the size and bulk of the Impulse Snorkel's mid-length bell-shaped chamber causes excessive drag when moving through the water, this problem is solved by the instant invention.